1. Field of the Invention
This invention relates generally to the catalytic conversion of hydrocarbon containing feed streams in the presence of a beneficial material that is dispersible in a hydrocarbon feed and product stream.
2. Description of the Prior Art
Numerous hydrocarbon conversion processes are widely used to alter the structure or properties of hydrocarbon streams. For example, hydrotreating is a common method for the upgrading of feedstocks by the removal of contaminants such as sulfur. Isomerization processes rearrange the molecular structure from straight chain paraffinic or olefinic hydrocarbons to more highly branched hydrocarbons that generally have a higher octane rating or increased utility as substrates for other conversion processes. Hydrocarbon dehydrogenation processes are well known methods of producing olefinic or aromatic substrates. Additional processes include alkylation, transalkylation, reforming and others. Operating conditions and methods for carrying out these process are well known by those skilled in the art. Well known methods for operating such processes include the adsorptive removal of contaminants from feed streams and the desorption of contaminants into resulting effluents or product fractions. U.S. Pat. No. 4,831,206 describes one such arrangement for the adsorption of sulfur compounds and is hereby incorporated by reference.
Many of these processes share the common feature of using a catalyst in the presence of one or more materials that enhance the effectiveness of the catalyst in the reaction zone. These performance enhancing materials can operate in many ways such as increasing or attenuating catalyst activity, neutralizing catalyst poisons, or solubilizing catalyst or feed contaminants. Such performance enhancement materials may be chemically or physically sorbed on the catalyst or dispersed in the hydrocarbon stream.
Where the hydrocarbon product stream leaving a hydrocarbon conversion zone contains the performance enhancing material or beneficent material, methods are sought for preventing contamination of the hydrocarbon product with the beneficent material and the loss of this beneficent material to the product stream. For example light paraffin dehydrogenation catalysts containing platinum, tin and germanium components have their activity attenuated with sulfur compounds. A description of such catalysts can be found in U.S. Pat. No. 4,786,625, the contents of which are hereby incorporated by reference. The effluent from the dehydrogenation zone can carry the sulfur compounds into downstream processes and products. Those skilled in the art will recognize a variety of other process where the materials useful in a catalytic conversion zone degrade products or process operations by their exit from the conversion zone into the effluent streams.
Isomerization of hydrocarbons presents another case where contamination of a catalyst promoter material poses concern. Many isomerization processes employ a highly effective chlorided platinum alumina catalyst system in the reaction zone. The chlorided catalyst requires a continual addition of chloride to replace chloride lost from the surface of the catalyst into the product stream. Hydrogen chloride and/or volatile organic chlorides escape from the process with a stabilizer overhead stream and, apart from the loss of chloride, pose environmental concern. In addition to the loss of chlorides and environmental concerns, chloride loss hinders the operation of chloride promoted isomerization zones in other ways. For example, the recycle of hydrogen or hydrocarbons by a zeolitic adsorption process is not practical when a chloride type catalyst is used unless hydrogen chloride is removed from the recycle stream. Hydrogen chloride produced by the addition of chloride to the reaction zone or released from the catalyst composite results in significant amounts of hydrogen chloride leaving the effluent from the isomerization zone. Contact of this hydrogen chloride with the crystalline alumino-silicates in adsorption or conversion zones will decompose the matrix structure of many crystalline alumino-silicates thereby destroying any catalytic or adsorptive function. Therefore, absent chloride neutralization methods, chlorided catalyst systems generally have insufficient compatibility with many zeolitic catalysts or adsorbents to permit simultaneous use.
A broad object of this invention is to recover and recycle materials which act to enhance the operation of catalytic conversion zones when such materials are carried from the conversion zone by a hydrocarbon effluent stream.
A further object of this invention is to improve methods the reaction of hydrocarbon feed streams with chloride promoted catalyst systems by retaining chloride promoter and minimizing chloride contamination of the product.
A yet further object of this invention is to improve methods for dehydrogenating C.sub.3 to C.sub.5 feedstreams that use sulfur compounds in combination with a multi-component catalyst in the reaction zone by minimizing sulfur product contamination.